Castellvi is a combat veteran of deployments to Panama, Somalia, Iraq and Afghanistan. He has held a variety of command positions and served in the Office of the Secretary of Defense and as a military assistant to the undersecretary of defense for policy in the Pentagon. He comes to the new post after serving as the chief of staff for the I Marine Division.

A native of Chicago, Castellvi earned his commission as a second lieutenant through the NROTC program at the University of Illinois.